The present invention relates generally to storage systems, remote copy systems, and data copy method of the remote copy system and, more particularly, to management methods to reduce the number of times of data transfer within the storage system.
Many products of storage system have remote copy functionality for disaster recovery. The remote copy functionality copies the data stored in a primary volume (storage area) in a primary storage system to a secondary volume in a secondary storage system. The remote copy is classified into two types: synchronous remote copy and asynchronous remote copy. The synchronous remote copy transfers the data synchronously with the write operation from the server, whereas the asynchronous remote copy transfers the data asynchronously with the write operation from the server.
U.S. Pat. No. 7,865,680 describes a data copy method of asynchronous remote copy. Asynchronous remote copy does not transfer the data to the secondary volume directory from the primary volume; rather, before storing in the secondary volume, it transfers the data to a buffer area. The buffer area is described as a journal volume. The buffer area may include cache memory. The reason for once transferring the data to the buffer area such as a journal volume is to assure data consistency by making a write order to the SVOL (secondary volume) and a write order to the PVOL (primary volume) from the server the same.
Because the data is transferred to the buffer in the asynchronous remote copy, a processing overhead will be large and the utilization efficiency of the hardware such as a cache memory will decrease. As a result, system performance will decrease.